The research proposed is an analysis in the chick embryo of 1) neural plate formation; 2) closure of the neural plate into a neural tube; 3) forebrain elongation and ventro-caudal reflection at the time of anterior neuropore closure; and 4) somite determination and patterning in forming-primative-streak stages. I will also (5) confirm the effect of low dosages of UV irradiation in stopping neural tube formation in the chick embryo and, by partial shielding or with a microbeam, localize the UV sensitive area in the neural plate. In chick and newt embryos, I will (6) analyse bulge and furrow formation in the expanding brain tube. For each of these six areas, I propose experiments, observations, and analyses to define the relative roles of various cell behaviors and changes, extracellular matrix, and supracellular mechanisms such as fluid pressures and tissue interactions. Approaches include light microscopy, SEM, TEM, time-lapse cinematography of marked embryos, effects of lectins, colchicine, and cytochalasin B, microsurgical rearrangements and explantations of tissues and tissue combinations, extracellular matrix analysis with strains, enzymes and light and electron microscopy, and measurements of regional tissue volumes through time. The goal of the research is to provide basic understanding of the physico-chemical mechanisms of morphogenesis. It is necessary to define the mechanisms and rules that govern normal formation of the nervous system and somites in order to understand such common human congenital malformations as spinal bifida, anencephaly, and hydrocephalus.